A switched reluctance motor is an electrical motor that includes a rotor and a stator. Torque in a reluctance motor is produced by the tendency of the rotor to move to a position relative to the stator in which the reluctance of a magnetic circuit is minimized, i.e. a position in which the inductance of an energized stator winding is maximized. In a switched reluctance motor, circuitry is provided for detecting the angular position of the rotor and sequentially energizing phases of the stator windings as a function of rotor position.
Switched reluctance motors are doubly salient motors having poles on both the stator and the rotor, with windings only on the stator poles. The rotor of a switched reluctance motor does not include commutators, permanent magnets, or windings. A switched reluctance motor may be used in a vacuum cleaner, for example.
Torque may be produced by energizing or applying current to the stator windings of the stator poles associated with a particular phase in a predetermined sequence. The energization of the stator windings is typically synchronized with the rotational position of the rotor. A magnetic force of attraction results between the poles of the rotor and the energized stator poles associated with a particular phase, thereby causing the rotor poles to move into alignment with the energized stator poles.
In typical operation, each time a stator winding of the switched reluctance motor is energized, magnetic flux flows from the energized stator poles associated with a particular phase, across an air gap located between the stator poles and the rotor poles, and to the rotor poles. Magnetic flux generated across the air gap between the rotor poles and the stator poles produces a magnetic field in the air gap that causes the rotor poles to move into alignment with the energized stator poles associated with a particular phase, thereby producing torque. The amount of magnetic flux and, therefore, the amount of torque generated by the switched reluctance motor is dependent upon many variables such as, for example, the magnetic properties of the material of the rotor poles and the stator poles, and the length of the air gap between the rotor poles and the stator poles.
The stator windings of the switched reluctance motor may be prewound around a bobbin. The bobbin acts as an insulation barrier between the stator windings and the core of the stator. The prewound bobbin may then be placed over each of the stator poles during motor assembly. Typically, vibrations in the motor structure, variations in motor temperature, and electromotive force (EMF) may cause radial displacement of the bobbin during motor operation, thereby causing undesirable acoustic noise.